The present invention relates to a V-belt type continuously variable transmission.
JP No. 60-249758 discloses a V-belt type continuously variable transmission wherein a power delivery path at the lowest speed ratio is established through a gear train, while a power delivery path at any speed ratio higher than the lowest speed ratio is established through a V-belt power transmission train.
In this known continuously variable transmission, a provision is made to secure a smooth shift between the lowest speed ratio and the adjacent next low speed ratio higher than the lowest speed ratio without any complicated sequence of switching operation of clutches. The provision is in that when a forward low clutch is established, the lowest speed ratio, namely a forward low gear position, is accomplished by engaging a forward low gear to an input shaft, thereby to establish a power delivery path through a gear meshing with this forward low gear and a one-way clutch, and a shift to the adjacent next low speed ratio higher than the lowest speed ratio is made when a forward high clutch is engaged with the forward low clutch kept engaged. According to this provision, the smooth shift from the lowest speed ratio to the adjacent next low speed ratio is effected with the forward low clutch kept engaged owing to overrunning of the one-way clutch.
According to this known transmission, a reverse gear train includes the above-mentioned one-way clutch. This arrangement of the reverse gear train does not transmit a reverse torque from road wheels to the input shaft since the reverse torque causes the one-way clutch to overrun. Thus, engine brake running is not provided when the vehicle travels in a reverse direction and down a steep hill-climbing road.
Therefore, an object of the present invention is to provide a V-belt type continuously variable transmission wherein the above-mentioned problem is eliminated with the smooth shift using one-way clutch maintained.